I wasn't just scrolling, I was actually clicking on menu, thumbnails and links but nothing works until it's fully loaded. Zeitreise theme loads after 3-4 minutes not sure why it's so slow, my internet is super fast, other websites load great. You can easily replicate this issue on your mobile - http://themes.elmastudio.de/zeitreise/.

I have the same problem described by Volodymyr.It doesn't have anything to do with customizations. It happens on many themes not just Zeitreise, also Hawea and Neubau on iOS 11.0.3.This makes the theme unusable, because it takes minutes until it's possible to navigate on the site.It seems to be an issue related to the loading bar. I tried disabling the javascript for it, but that made the site unusable on every browser, because no links were clickable.

I'm still not able to reproduce this behavior. Since Volodymyr mentioned it may be a problem with iOS itself, emptying the browser data including its cache may solve the problem. Unfortunately currently the theme demos are running an older version of the themes.